JP2017078861A - Bezel-free display device using directional backlight - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bezel-free display device.SOLUTION: A bezel-free display device comprises: a directional backlight 44; a diffusion member 16a; a display panel 12 that is arranged between the directional backlight 44 and the diffusion member 16a to display images; and a backlight diffuser 74 that is arranged between the directional backlight 44 and the display panel 12. The divergence half angle of light radiated from the directional backlight 44 does not exceed 15° with respect to a normal of a plane of the display panel 12, and the backlight diffuser 74 does not extend to the opposite edge parts of the display panel 12.SELECTED DRAWING: Figure 13

Description

Explanation of related applications

  This application claims the benefit of the priority of US Provisional Patent Application No. 61 / 608,960, filed March 9, 2012, the contents of which are incorporated herein by reference in their entirety. Claims under Article 119.

  The present disclosure relates to bezel-free displays, and more particularly to bezel-free liquid crystal displays that incorporate directional backlights.

  In this document, the term display device includes, but is not limited to, laptops, notebooks, tablets, desktops, and other computers, cell phones, televisions (TVs), etc. that are capable of displaying visual content. It is intended to encompass these devices. Each of the aforementioned devices includes many components, such as a physical case or cabinet in which individual components may reside, circuit elements such as circuit boards, integrated electronics, and of course the display panel itself. Currently, such display panels include liquid crystal display elements, organic light emitting diode (OLED) display elements, or plasma display elements, and, of course, glass or plastic substrates that surround and / or place many of these elements. It is a flat display panel provided with. Typically, the edge portion of the flat display panel and the display device itself is a variety of other conductors related to the operation of the display panel, such as conductors and circuitry that drives the pixels of the panel, and in the case of LCD display panels, LED illuminators. Used for electronic components. For this reason, flat display panel manufacturers have placed the edge portion inside and / or behind the bezel. The bezel helps to hide the aforementioned components, but it also covers the edge of the display panel and reduces the overall image size.

  For aesthetic reasons, flat panel display manufacturers strive to maximize the display area of the image to provide a more aesthetic appearance and thus minimize the size of the bezel surrounding the image. However, there is a practical limit to this minimization, and the width of the current bezel size is about 3 mm to 10 mm. Therefore, to achieve the ultimate goal of having no bezel at all, observe the impression that the image occupies the entire panel surface while reducing the gap between the imaging display panel and the display cover plate A visual solution has already been proposed.

  According to the embodiments described herein, the display device is given a bezel-free appearance, for example by employing a diffusing member and a directional backlight.

  In one example embodiment, a display device is disclosed, the display device being positioned between a directional backlight, a diffusing member, a directional backlight and a diffusing member, and configured to display an image. A display panel, a bezel disposed around the display panel, and an image magnifier configured to conceal the bezel by magnifying the display panel image, and the divergence half-angle of the light emitted from the directional backlight is It is characterized by not exceeding 15 ° with respect to the normal of the plane of the panel. In the case of an LCD display panel, the display panel comprises, for example, a first substrate, a second substrate sealed to the first substrate, and the LCD material is positioned between the first substrate and the second substrate. . These substrates are typically formed from glass. The display panel may further include various thin film materials deposited on one or both of these substrates, including but not limited to transparent thin film transistors, polarizing films, color filter films, ITO (indium tin oxide), etc. Examples include conductive films, antireflection films, spacer elements, and alignment films.

  The diffusing member may include, for example, a display cover plate positioned between the display panel and an observer of an image formed with the display panel. The diffusing member may have diffusing particles distributed inside the substrate below the surface of the substrate, such as inside the body of the substrate. In some examples, the average particle size of the diffusing particles is between 100 nm and 300 nm. In other examples, the average particle size of the diffusing particles is in the range of about 150 nm to about 250 nm. In some examples, the display cover plate includes glass. This glass may be chemically strengthened glass such as ion exchange glass. The display cover plate may include a light absorbing layer that includes an array of transparent regions. The directional backlight may comprise a diffusing screen that does not extend to opposing edge portions of the display panel. The separation membrane may be positioned on the edge portion of the display panel.

  These and other aspects are better understood when the following detailed description is read with reference to the accompanying drawings.

Front view of display device with display panel and bezel Front view of tiled array of display devices Front view of display cover with prism area to hide bezel FIG. 6 is a schematic view of a portion of a prism region positioned on the outer surface of the display cover plate 16 (facing the viewer), showing the individual prisms. Graph showing prism angle θ as a function of position on display device Schematic showing an observer positioned away from the display panel of a display device covered with a bezel concealed display cover A plot of the ratio of gap distance D to bezel width W as a function of prism angle θ FIG. 6 is a cross-sectional view of the edge portion of the display cover plate including the prism array positioned in front of the bezel and the display panel with respect to the display panel viewer, showing how the display panel is seen by the viewer Sectional view showing a portion of the display panel and bezel, and a single prism of the prism array of FIG. Sectional view of a display device including a diffusing member positioned between the display panel and an observer An enlarged view of a portion of the edge portion of the display device, including a diffusing member positioned between the display panel and the viewer FIG. 2 is a cross-sectional view of a portion of a diffusing member positioned between a display panel and an observer, the diffusing member comprising a lens array and the substrate comprising an absorbing layer containing an aperture, through which light can be transmitted Diagram showing that Cross section of directional backlight including light guide plate Partial sectional view of light guide plate and turning film FIG. 4 is a cross-sectional view of a portion of a display device, showing that a diffusing member is used with a backlight and a portion of the diffusing screen is removed from the backlight to create a directivity of the emitted light. It is the enlarged view of the edge part of the display apparatus of FIG. 13, Comprising: The figure by which the turning film is arrange | positioned on the diffusion member FIG. 3 is a partial cross-sectional view of a diffusion member, in which diffusion elements (for example, particles) are dispersed in a diffusion layer inside the diffusion member Graph showing normalized scattering cross section as a function of scattering angle at a particle size of about 25 μm Graph showing normalized scattering cross section as a function of scattering angle at a particle size of about 200 μm Graph showing the normalized scattering cross section as a function of scattering angle at a particle size of about 500 μm

  Examples will now be described more fully hereinafter with reference to the accompanying drawings, in which example embodiments are shown. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. However, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

  The beauty of display devices such as television display panels, computer monitors, and laptop display panels is affected by the size and appearance of the bezels that exist around these display devices. For example, a display device bezel can be used to house electronics for driving the pixels of the display panel and possibly provide a backlight for the display device. For example, an LCD television display panel may include a plurality of backlighting light emitting diodes (LEDs) held within the bezel region of the display device.

  In the last few years, the bezel has become increasingly smaller. The current bezel width is about 3 to 10 mm. However, in a television model with a very large display panel, a narrow bezel region was realized that was 2 mm wide at least two edges and 4 mm wide at the other two edges. However, the presence of the bezel, even if it is small, is still distracting, especially when the display device is assembled in a tiled arrangement to form a very large display image. Such a bezel of a tiled display device gives an undesired appearance of an image “grid”, rather than a large, tight, seamless image. The eyes are very sensitive to the presence of black lines that divide the tiled display device, making these images unsightly.

  Embodiments of the present disclosure include a bezel concealment display cover plate that conceals the bezel so that the presence of the bezel is not visible, or at least not easily noticed by the viewer within a predictable viewing angle. . The display cover plate may be formed from glass, for example. In some embodiments, the glass may be a chemically strengthened glass.

  Referring now to FIG. 1A, a display device 10 configured as a flat display panel television is illustrated. It should be noted that although the following description is primarily directed to a television, the embodiments described herein may be suitable for other display devices, and thus the described embodiments are not limited to televisions. The display device 10 includes a display panel 12, and the display panel 12 has a bezel 14 positioned around it. Bezel 14 includes bezel portions 14a-14d. In addition to the display drive electronics, the bezel portions 14a to 14d can include backlight equipment such as edge light emitting diodes (LEDs) for applying backlight to the display panel 12. The bezel portions 14a-14d may have a certain width, such as between 3 mm and 10 mm. In particular, as shown in FIG. 1B, the bezel portions 14a-14d can be distracting to the viewer when several display devices are arranged in two dimensions to view the entire image.

  One method for realizing such a bezel concealment characteristic is configured by placing a magnifying optical element such as a Fresnel lens as shown in FIG. 2 at a predetermined distance from the display panel. The Fresnel lens has an optical structure such as a microprism. The lens structure may be, for example, a plastic film attached to the display cover plate 16. In order to minimize the gap distance between the display panel and the lens (eg display cover plate), the prism is required to introduce very high beam deflection. However, if the beam incidence at the prism is extremely steep, total internal reflection may occur on the prism surface. In order to avoid this, the deflection angle introduced by the prism should be limited. This leads to the requirement for very large air gaps (typically 4-5 times the bezel width). However, by using a directional backlight and a diffusing surface on the display cover plate, the size of the air gap can be reduced to less than about 4 times the bezel width.

  The bezel concealment display cover plate 16 may include, for example, a prism region including four prism portions 18a to 18d adjacent to the periphery of the display cover plate. As will be described in more detail below, the prism portions 18a-18d are an array that acts as a light bending (refractive) filter for the region of the display panel 12 located behind the bezel portions 14a-14d for the viewer. Including many prisms arranged in The light bending filter provided by the display cover plate and the prism portions 18a-18d prevents the bezel from being visible, or at least within a predictable viewing angle, so that the bezel is not easily visible to the viewer. Allows you to hide the bezel. The bezel concealment display cover plate 16 may further include a visually transparent central portion 20 bounded by the prism portions 18a-18d. This central portion 20 does not contain any prisms and is therefore substantially flat. The bezel concealment display cover plate 16 may be made from glass. For example, the glass may be chemically strengthened glass such as ion exchanged glass, acid washed glass, or both. The prism portions 18a-18d may be made from commercially available optical bending filter materials that can be adhered to the display cover plate, such as, for example, Vikuiti image directing film (IDF II) manufactured by 3M. Good. It should be understood that Vicuity is just one of many possible light bending filter solutions and is presented here as a non-limiting example only. In another example, a light bending filter may be incorporated directly into the display cover plate 16. For example, the prisms may be formed directly on the display cover plate material. As described in more detail below, special light bending filters can be optimized and developed to hide the bezel from the viewer. It should be noted that when using a Vicity optical bending filter, an air gap of approximately 2.7 times the desired lateral image shift is required.

  Referring now to FIG. 3A, a portion of the positioned prism region 18 of the bezel concealment display cover plate 16 is shown. The prism portion includes a number of prisms 22 formed in a triangular shape. In this figure, the prism 22 is positioned on the outer surface of the display cover plate 16 (facing the viewer). The prism 22 includes a prism angle θ that shifts the image near the bezel. This prism angle is an angle sandwiched between prism surfaces (facets) through which light mainly passes when passing through the prism. FIG. 3B is a graph showing the prism angle θ as a function of position on the display device 10. In general, the angle θ of the prism 22 should be maximum at the edge of the bezel concealed display cover plate 16 and decrease to zero (ie, all of the prism is gone) away from the edge of the display cover plate. Therefore, only a small part of the image generated on the display panel 12 is shifted. The frequency of the prism array, i.e. the periodicity of the prisms, should be greater than the frequency of the pixels of the display panel so as to prevent aliasing of the resulting image. In general, the prism should be smaller in size than the pixel. For example, each prism may be as small as 1/10 of one pixel size.

  The solid curve 24 shows an example in which the prism angle θ decreases linearly from the edge of the bezel concealed display cover plate 16 and becomes zero in the central region beyond the distance d. A dotted curve 26 shows an example in which the prism angle θ of the prism changes nonlinearly over the distance d. More complex dotted curve 26 profiles can be considered to prevent disastrous image discontinuities.

  FIG. 4 schematically shows an observer O located far from the display panel 12 of the display device 10, with a bezel concealed display cover plate 16 positioned between the display panel and the observer. ing. A gap D exists between the bezel concealing display cover plate 16 and the display panel 12. The simulation tracks the light emitted from the display panel 12 to the viewer O, and for a given position X1 on the display panel 12, shows the position X2 where the light hits the bezel concealed display cover plate 16. In one simulation, the prism faces the viewer O and the prism angle of the prism is from 32 ° at the very edge of the bezel concealed display cover plate 16 (ie, just above a portion of the bezel 14) to the outside of the display cover plate 16. It changes linearly to 0 ° at a position about 10 mm away from the edge. The refractive index of the bezel concealed display cover plate 16 in the simulation was 1.5, and the gap D was about 15 mm.

  The amount of beam deflection that can be produced by the prism is a function of the prism angle θ. The graph shown in FIG. 5 assumes that the refractive index is 1.5, and further assumes that the bezel can be essentially invisible at a viewing angle of about 20 °, and that the gap relative to the bezel width W. The ratio of D is shown as a function of the prism angle θ. As an example, using a prism angle θ of about 45 °, the air gap needs to be at least four times the width of the bezel (ratio 4).

  Note that the local light bending filter provided near the bezel of a display device such as display device 10 by the example of the bezel concealment display cover plate 16 described above can cause image distortion. Such image distortion can be reduced, for example, by changing the pixel position in the display device to compensate for optical distortion introduced by the prism. If the prism angle variation is a linear function, it can be shown that image distortion causes local enlargement of the image, which is compensated by using a smaller pixel pitch at the edge of the display device. Can do.

  When the observer is not viewing the display device 10 at normal incidence, the bezel 14 may be partially or completely visible. In particular, when the observer O is very close to the display device 10, the observer will see all edges of the display cover plate at a high incident angle, so that all the bezel parts are visible. For example, the impression that the television is in the box can be given.

  The visibility of the bezel when the viewing angle is increased can be reduced by adding a diffuse texture to the prism portions 18a-18d of the bezel concealed display cover plate 16. Because this portion of the image is generated on the bezel concealed display cover plate 16, the image may be partially blurred in this region near the bezel portions 14a-14d. However, the observer's attention is usually fixed near the center of the image, and the surrounding information is not important. Therefore, even if there is a 10 mm blurred area on a large TV, there is no visual distraction. Let's go. In some examples, the prism portions 18a-18d may have prisms on each side of the bezel concealed display cover plate 16 to increase the viewing angle.

  Referring now to FIG. 6, the edge portion of the bezel concealed display cover plate 16 is shown having a curved portion 28 that covers the bezel 14 in close proximity to the edge of the display device 10. The curved portion 28 includes a prism 22. The shape of the curved portion 28 of the bezel concealment display cover plate 16 is optimized to conceal the bezel 14 over a wider viewing angle. The prism 22 may be formed directly on the display cover plate 16 or may be formed on a film attached to the display cover plate 16 or other processes may be employed to make small prisms on the display cover plate 16. A structure can also be realized. This allows a visually bezel-free image to be generated with a very large viewing angle, for example 45 ° as a non-limiting example.

  In the embodiment depicted in FIG. 6, a portion of the bezel concealed display cover plate 16 is shown, including a light bending filter 30 having a plurality of prisms 22 facing the display panel 12. The display cover plate 16 has a first straight central portion 20 at a position slightly away from the display panel 12, thereby providing a gap D between the display cover plate 16 and the display panel 12 of the display device 10. The The display cover plate 16 further includes a curved portion 28 connected to the central portion 20. Line 32 depicts how the viewer O will see the image formed by the display panel 12 and shows how the image is stretched (eg, shifted) on the bezel 14.

  Reference is now made to FIG. 7 showing a single prism of the optical bending filter of FIG. 6 with the prism 22 facing the display panel 12. When the image is observed at a relatively large negative angle γ along the dotted line 40 with respect to the 0 ° observation position indicated by reference numeral 30, the angle β of each prism relative to the facet 42 at the prism-atmosphere interface is Very small. If the angle β continues to decrease, the angle β reaches the angle of total internal reflection which means that the image of the display panel 12 is no longer visible from the viewer. For example, when the viewing angle γ of an image having no defect is set to −60 °, the maximum prism angle θ for avoiding the total internal reflection state is about 6.5 °. In order to prevent the bezel from being seen at normal incidence in this case, the air gap D needs to be approximately 18 times larger than the bezel width.

  One approach to addressing total internal reflection and increased viewing angle range is to optimize the prism angular variation profile. With curved glass, the gap distance D can be minimized, but to obtain a large viewing angle without any distracting visual artifacts, a typical minimum gap is approximately 5 times the bezel width. Modeling has shown that

  The basic limitation of some of the approaches described above is that a large deflection is required, but also that a prism is required to work for a very wide range of viewing angles. Next, a display panel as shown in FIG. 8 will be considered. Light emitted from the backlight 44 and passed through the display panel 12 toward the viewer O passes through an image enlarging device 46 such as a diverging Fresnel lens array 48 and a converging Fresnel lens array 50. In this case, when the prism 22 is inserted into the optical path, the prism is effective for a particular viewing angle. Thus, the system is optimized at that angle, and the prism can achieve great deflection without causing total internal reflection of light incident at the interface between the air gap and the prism. However, since the light emitted from the display panel 12 is transmitted only in one preferred direction, the image can be clearly seen from the observer O with only one viewing angle. Accordingly, the viewing angle may be widened by positioning the diffusing member 16a between the image enlarging device 46 and the observer O. The diffusing member 16a may be, for example, the display cover plate 16 configured to diffuse light.

  Since the diffusing member 16a is introduced at a predetermined distance from the pixels of the display panel 12, the image may be easily blurred. The magnitude of this blur can be determined up to the first approximation by the following equation.

B = 2Dtan (Ψ) (1)
Where B is the amount of blur, D is the air gap distance from the display panel to the diffusing member, and Ψ is the divergence half-angle of the light emitted from the backlight 44 relative to the normal of the plane of the display panel 12. In order to minimize the amount of blur, a backlight with a high degree of directivity is required, that is, a small divergence half-angle is required. Furthermore, the air gap distance D should be minimized if the beam deflection near the edge of the display panel is large. In this document, a directional backlight is a backlight in which the divergence half-angle of the light emitted by the backlight is about 15 ° or less with respect to the normal line of the plane of the display panel in which it is used. In some examples, this divergence half angle may be 10 ° or less. In other examples, the divergence half angle may be less than 5 °.

  In some embodiments, the gap D between the display panel 12 and the diffusing member 16a only occurs at the edge position of the display device 10 where the bending optics are positioned to enlarge the image. In this case, the diffusion member 16a is in a state of being in close proximity to the display panel 12 at a position covering most of the display panel surface, and blurring of the image appears only at the position of the very edge of the image.

  In another embodiment, the backlight 44 needs to be directional only near the edge of the display panel 12. Accordingly, as shown in FIG. 9, a diffusing member 16a may be provided that affects only the edge portion of the transmitted image. FIG. 9 shows the area of the display device near the edge of the display device and the diffusion member at that position protruding away from the display panel 12 near the edge of the display panel. In this case, neither the directional backlight nor the diffusing member is required in the remaining image transmission process.

  If a conventional diffusing member is positioned between the display panel 12 and the viewer O, the contrast of the image may be affected by haze. Therefore, as opposed to the scattering material disposed on the surface of the diffusing member, a bulk scattering element (that is, particles contained inside the main body of the diffusing member) is employed (see FIG. 15) to reduce image blurring. May be.

  In another example, the display device 10 as shown in FIG. 10 includes a diffusing member 16a, preferably in the form of an array 54 of random and generally anamorphic microlenses 58, a substrate (eg, display cover plate 16), And a light-absorbing material layer 60. For example, the light absorbing material layer 60 may be formed on the back surface of the diffusion member facing the display panel 12. The diffusion member can be formed using the following process. In the first step, the microlens array, the substrate, and the light-absorbing material layer may be combined into a single sheet (if desired, the microlens array and the substrate may constitute a single unit). . In the second step, the substrate is exposed to aperture-forming illumination, such as ultraviolet light, through the microlens array itself, creating an aperture in the light absorbing material. There is no need to use an external alignment mask, and the initial self-alignment provides effective transmission of light through the aperture. The microlens array can be designed such that the aperture generated by the aperture-forming illumination does not block any portion of the useful luminosity energy from the backlight 44. At the same time, the microlens array 54 may be designed to maximize the density of light absorbing material remaining after aperture generation. The aperture means a physical aperture (hole) or a transparent area in the light absorbing material. The specific case depends on the interaction between the light-absorbing material and the aperture-forming illumination, for example this interaction can cause ablation or photochemical reaction. Since the light from the directional backlight is substantially parallel (that is, the collimated light 56), the light beam collected by each microlens 58 of the microlens array 54 is focused on the diffusing member 16a. The light absorbing material can be positioned with respect to the microlens array so that the screen can produce an acceptable image while minimizing the size of each aperture. In the above example, the majority of the surface of the display cover plate 16 includes an absorbent layer, so that the visible glare can be significantly reduced.

  According to the above example, the distribution of light through the diffusing member 16a includes an array of spots having a size given by the following equation:

r = f · θ (2)
Here, r is the radius of each spot, and f is the focal length of the microlens array 54.

  In cases where only two bezel portions such as bezel portions 14a and 14b require concealment, a unidirectional backlight may be used. However, in order to avoid blurring of the image, the diffusing member should be such that light is diffused only in the horizontal direction. Such a diffusing member can be produced, for example, by a holographic method, and can be replicated on a plastic sheet at a low cost. Furthermore, since the light is directional only along the X axis, the microlens array 54 of the diffusing member including the light absorbing layer such as the diffusing member 16a in FIG. 10 must be replaced with an array of cylindrical lenses. The diffusing member 16a is then formed to have a transparent slit aperture instead of an array of transparent circular apertures.

  The current trend in high quality backlights for LCD display panels consists of using a side lighting design as depicted in FIG. 11 where the light guide plate 62 is a wedge-shaped plate, which is edged by the light source 64. Illuminated from. For example, the light source 64 may be a plurality of light emitting diodes. Alternatively, the light source 64 may be a cold cathode fluorescent lamp. In order to extract light from the light guide plate 62, the light guide plate is positioned at a predetermined angle with respect to the display panel 12. Alternatively, the light guide plate may include an array of prisms having a very shallow angle with respect to the display panel. The light propagates into the light guide plate 62, reflects a large number of light, and is at least partially extracted from the light guide plate. Although only a single light ray is shown, a number of light rays enter the light guide plate 62 at various angles, so that for the light source 64 light will leak from the light guide plate along the length of the light guide plate. . In order to capture and reflect light that may leak from the back surface of the light guide plate 62, a reflector 66 may be provided behind the light guide plate 62 for the observer. When such a structure is simulated with discontinuous ray tracing, it is found that light leaks at a very high angle χ in the range of about 80 ° to 90 °. Here, a dotted line 68 represents a normal line of the plane of the display panel 12, and χ is a divergence half angle of light emitted by the light guide plate 62. As shown in FIG. 11, an additional film, such as turning film 70, may be used to refract the light closer to normal incidence.

  As shown in FIG. 12, the turning film is composed of an array of prisms 72, which are arranged such that one face of each prism provides total internal reflection of incident light and bends the light. Yes. An example of a suitable turning film is the Vikuiti ™ turning film (ie, TRAF II) manufactured by 3M Company. FIG. 12 shows a number of light beams propagating through the light guide plate 62. The turning film 70 shifts the direction of light or rays that would normally be glazed in the absence of the turning film to substantially normal incidence with a relatively narrow radiation half angle χ (eg, 5 °), depending on the angle of the light guide plate 62. Let In some examples, a plurality of turning films may be employed in combination, with the turning films being “oriented” in various directions.

  Conventional LCD displays typically require that the light emitted by the backlight 44 be as close as possible to Lambertian radiation so that the image can be viewed at a large viewing angle without significantly reducing the intensity. . As a result, a typical backlight includes a backlight diffuser 74 that functions to disperse the light within a wider angular range in both the X and Z directions. By removing the backlight diffuser 74 from a conventional backlight, a unidirectional backlight can be easily formed.

  FIG. 13 depicts the structure of a certain system. In this system, at least a portion of the backlight diffuser 74 (eg, diffusing film) is removed near the edge of the display panel so that the light from the backlight 44 is perpendicular to the plane of the display panel near the edge of the display panel. The backlight 44 resembles a Lambertian diffuser across most of the display panel 12 except that it has a high directivity in the Z direction.

  At the edge of the image where the backlight 44 is directional by removing at least part of the backlight diffuser 74, a separation membrane comprising a series of microprisms used in total internal reflection mode and having a duty ratio of 50% 76 is inserted. That is, approximately 50% of light (reference number 78a) passes directly through the film, and 50% of light (reference number 78b) is refracted (turned) by the film at a large angle. The diffusing member 16a is inserted into the optical path to scatter light, thereby generating an image that can be viewed over a wide viewing angle.

  When the light is separated by the separation film 76, the light needs to be "straight" and scattered (see FIG. 14). Using the diffusion principle described above, modeling has shown that the air gap D can be less than or equal to the bezel width, and in some cases can be less than about 0.7 times the bezel width. According to the above-described embodiment, a diffusive element may be formed on the display cover plate 16 to form the diffusing member 16a as a diffusive film (ie, layer) formed by, for example, a holographic film process. Alternatively, a diffusive element may be formed inside the display cover plate 16 (under the surface).

  As shown in FIG. 15, a high scattering index element 82 (eg, particles) located below the surface 84 of the display cover plate may be used to form the volume scattering region 80. FIGS. 16-18 illustrate the effect of the size of the scattering element on the size of the scattering, showing the normalized scattering cross section as a function of angle. As shown in FIG. 16, scattering elements on the order of 25 nm in diameter provide too much backscatter. The curve in FIG. 16 shows a high forward scattering intensity (ie at an angle of 0 °), but also shows a large scattering at an angle of 180 ° and represents a high backscatter. On the other hand, FIG. 17 shows that a scattering element 82 on the order of 200 nm in diameter provides mainly forward scattering over a fairly wide angular distribution (eg, 0 ° to 45 °). Finally, FIG. 18 shows a dominant forward scattering peak at a relatively narrow forward scattering angle for a scattering element 82 of about 500 nm in diameter (eg, less than about 20 °). Thus, in the examples of the present disclosure, the average particle size of the scattering elements ranges from about 100 nm to about 300 nm, and in other examples ranges from about 150 nm to about 250 nm.

  It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the claimed invention.

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display panel 14 Bezel 16 Display cover plate 16a Diffusion member 18 Prism area | region 20 Center area | region 22 Prism 44 Backlight 56 Collimated light 60 Light absorption material layer 80 Scattering area | region 82 Scattering element

Claims (8)

In the display device,
Directional backlight,
Diffusion member,
A display panel disposed between the directional backlight and the diffusing member and configured to display an image;
A bezel disposed around the display panel; and a backlight diffuser disposed between the directional backlight and the display panel;
With
The divergence half-angle of the light emitted from the directional backlight does not exceed 15 ° with respect to the normal of the plane of the display panel;
The display device according to claim 1, wherein the backlight diffuser does not extend to opposing edge portions of the display panel.   The display device according to claim 1, wherein the diffusion member includes a display cover plate.   The display device according to claim 2, wherein the display cover plate includes glass.   The display device according to claim 3, wherein the glass is chemically strengthened glass.   The display device according to claim 2, wherein the display cover plate includes a light absorption layer including an array of transparent regions.   The display device according to claim 1, further comprising an image enlargement device disposed between the display panel and the diffusion member.   The display according to any one of claims 1 to 6, wherein a separation film is disposed on the edge portion of the display panel, and a duty ratio of the separation film in the total internal reflection mode is 50%. apparatus.   The display device according to claim 1, wherein the diffusion member includes diffusible particles distributed inside the substrate.